The present invention relates to manual control devices for operating machinery, and in particular to dual axis "joystick" type control devices for use in operating hydraulic valves.
Construction and agricultural equipment often employ a control device which the operator manipulates to control movement of a member that is driven by hydraulic actuators. One type of such control devices is commonly referred to as a "joystick." A single axis joystick has a handle which is pivoted in one direction to open a valve and is pivoted in an opposite direction to open another valve thereby controlling flow of hydraulic fluid to a bidirectional actuator. A dual axis joystick may be pivoted about two orthogonal axes to operate valves that control movement of the member about two axes.
In both versions, the control device has a neutral position in which the handle is vertical. Movement in either direction from vertical about a given axis operates a different valve causing the associated actuator to move in the corresponding direction. The valves or the mechanical linkage between the control device and the valves are biased by springs which cause the control device to return to the neutral position upon being released by the operator. Therefore, in order to maintain the valve in a given position the operator must constantly apply force to the joystick handle in order to prevent the control device from returning to the neutral position.